The present invention is broadly concerned with a jig for straightening a metal vehicle frame or body. More particularly, it is concerned with a portable folding jig used in connection with a plurality of pulling towers for simultaneously exerting pulling forces on a vehicle from multiple directions, several pulling towers being positionable on the same side of a vehicle.
Serious collision damage to vehicles such as cars, trucks and sport utility vehicles generally includes misalignment of the frame or unibody structure. The nature and extent of such misalignment may be determined using a centerline gauge to read and record a series of measurements, which are then compared with manufacturers' published vehicle dimension specifications. This enables determination of the severity of under-body damage and mapping of its various locations. The frame damage is then repaired by attaching a pulling tower or power post assembly to a point on a vehicle frame or unibody structure and actuating a hydraulic ram to pull the deformed portion of the frame and body into alignment. By performing a series of pulls, the chassis including the frame or unibody may be returned to its proper dimensions and alignment.
Large, bench-type frame machines may be employed to secure the vehicle during this procedure. These machines typically include a drive-on supporting platform or table with a series of apertures spaced around the perimeter for attachment of a pulling chain which is actuated by a pulling tower. The vehicle is supported above the table by clamps to the pinch weld of a unibody, and the chains are hooked to the damaged sections. Fixed beams are coupled with the table, and are capable of mounting multiple pulling devices. These bench-type machines are powerful and effective, and they permit a full range of movement of the pulling devices to any position around the vehicle. The pulling towers can be positioned side-by-side, on one side of the table for straightening side damage to the vehicle. But these machines are expensive to purchase as well as to operate, since technicians must be trained in their use. They take up a full bay in a body shop and are too heavy and cumbersome to be moved about when not in use.
Floor mounted platform systems have been developed which provide a somewhat cheaper alternative. In these systems, the platform is bolted to the shop floor and so-called “floor pots” are cemented into the floor at preselected locations for coupling with the pulling towers. These systems do not stand as high as the larger frame machines because they do not include structure for lifting the vehicle. They are large, however, taking up a full bay, and they require permanent installation.
Alternatively, an individual post-type pulling device can be chained between a floor pot and the vehicle and actuated to pull one damaged section of a vehicle at a time while the vehicle remains on the floor. Such portable towers are well-suited to exert pulling force along the longitudinal axis of the vehicle. However, in order to provide a range of pulls, they must be moved about the vehicle. They are not well configured to perform side pulls, since multiple devices cannot be positioned on one side of a vehicle, and they do not make lower pulls with the power of the larger machines. Mechanics dislike working with such devices on the floor, as access to the underside of the vehicle is limited and inconvenient.
In recent years there have been attempts to develop portable frame straightening machines or jigs that permit attachment of pulling towers to a portable base. Such jigs permit simultaneous attachment of more than one pulling tower, like the big machines, but the towers have a limited range of motion. In order to provide a range of pulls, the base and towers must be disengaged and repositioned. Such machines also do not permit attachment of the towers adjacent each other on one side of the vehicle, for example, to perform a side pull using multiple towers. They also do not permit attachment of multiple towers at each end of a vehicle. A particular advantage of such portable frames is that they can be stowed in a convenient location when not in use.
There is still a need for an economical, portable jig that provides the complete range of pulls as well as simultaneous pulls from the same side of a vehicle that have previously been available only with large platform collision repair systems.